1. Field of the Invention
The present invention relates to apparatus for producing multi-component plastic foam for use in undergound coal mining, particularly for fire fighting.
2. Background of the Invention--Description of the Prior Art
Foam generating apparatus is used in underground mines to improve fire prevention capabilities. The foam can be employed for closing off cavities through which firedamp (methane) is emerging, which could otherwise cause spontaneous combustion of coal. This is particularly important in the case of abandoned galleries, as there is always enough coal remaining for spontaneous combustion to occur, so long as sufficient oxygen is available. Cavities caused by roof falls or produced during the driving of galleries can also be filled using such means, to avoid the development of pockets of firedamp and other dangerous gases.
Closing off with plastic foam is considerably more cost and time saving than using rubble or other materials. On the other hand, because of the relatively high cost of plastics, the filling of such cavities is restricted to those which are not constantly swept through and kept clear by passing air current.
The components of the foam, typically a resin and a foaming agent, are withdrawn from storage vessels and provided to a spray unit by means of compressed air and pipelines. The components are mixed and distributed by the spray unit to seal off the cavity.
Unitary foaming apparatus incorporating the storage vessels, air compressor, pumps, and spray gun in a single unit tends to be so large and bulky that its utilization in mines is restricted because of the small spaces occurring in many places in the mine. This is a serious limitation because fire hazards which the foam barricades protect against often occur in such small spaces.
For this reason, foaming apparatus has been developed employing pumps which may be individually carried to the site. With the usual two-component plastic foam, two separate pumps are necessary, one for withdrawing the resin and the other for withdrawing the foaming agent from the storage vessels. The pumps deliver the resin and foaming agent to the spray unit which is of pistol-like form. While this permits more widespread use of the foam generating equipment, the time necessary to connect the pumps, material containers, air compressors, spray unit, etc. together greatly reduces the rapidity with which the foam can be emplaced, particularly in view of the cramped spaces, high temperature, dust, and darkness of the mine. On account of the same reasons, and because of the complexity of the equipment, the danger of accidental interchange of the components, particularly the pumps, is also quite high. This leads to considerable contamination or even damage to the pumps which can then only be used again after a thorough cleaning.
So far, such a plant can not be carried and operated by one man alone, although it can be broken down into individual portable parts and accessories. The weight of such plants amounts to around 12 kg. Thus, one man can only carry one pump in each hand and a second man must carry and operate the accessory parts, i.e. the pipes, the spray unit, and the containers for the resin and foaming agents.